Synergy effects in binary and ternary mixtures of inhibitors in polypropylene autooxidation

The autooxidation of solid isotactic polypropylene, inhibited with three di fferent additives, a phenol, an amine and a nitroxyl radical as well as the ir binary and tertiary mixtures was investigated. Noticeable synergy effect s were observed for phenol-amine and phenol-nitroxyl radical combinations; these effects were especially high in the region of low inhibitor concentra tion-the so-called subcritical region. A mathematical model is proposed for evaluation of the contribution of each inhibitor to the induction period. The value of such a description was confirmed by comparison of the experime ntal and calculated data. (C) 1999 Elsevier Science Ltd. All rights reserve d.